Many English speakers do not know the difference between who and whom. In some places, it hardly matters, because using who when you should use whom is so common that it's not even considered much of a mistake. But for those who want to know the difference between who and whom, here is an explanation

Grammar

Wh- questions are so called because with the exception of the question word how, all the question words begin with the letters Wh. They are also called open questions because the number of possible responses is limitless.